The present invention relates to a thermal transfer recording medium for forming a multi-color image by superimposing printing of a plurality of colored inks.
Hitherto, the formation of a multi-color image (including a full-color image, hereinafter the same) has been carried out by superimposing a plurality of heat-sensitive color inks on an image receiving sheet with use of a thermal transfer printer or the like. Also, as a thermal transfer recording medium for this purpose, those having a structure in which a release layer composed of a wax as a main component is provided between a substrate and a color ink layer in order to provide excellent transferability have widely been used.
However, in the case that a multi-color image is formed by superimposing a plurality of different color inks using thermal transfer recording media with the foregoing structure, the release layer composed of mainly a wax would exist on the top of first color ink dots formed on an image receiving sheet, and as a result, at the time of transferring second color ink dots, there takes place a problem that the release layer composed mainly of a wax on the top of the first color ink dots is melted so that the second color ink dots do not satisfactorily adhere to the first color ink dots.
In view of the aforesaid problem of the prior art in the case of forming a multi-color image by superimposing printing of a plurality of different color inks using thermal transfer recording media each having a structure in which a release layer composed of a wax as a main component is provided between a substrate and a color ink layer in order to provide excellent transferability, it is an object of the present invention to provide a thermal transfer recording medium or a combination of thermal transfer recording media capable of satisfactorily transferring second color ink dots onto first color ink dots.
Another object of the present invention is to provide a method for forming a multi-color image using the forgoing thermal transfer recording medium or combination of thermal transfer recording media.
These and other objects of the present invention will become apparent from the description hereinafter.
According to a first aspect of the present invention, there is provided a color thermal transfer recording medium for forming a multi-color image by superimposing printing of a plurality of different color inks, comprising a substrate, and at least a first color transfer layer and a second color transfer layer provided on the substrate in a side-by-side relation,
the first color transfer layer comprising at least a first release layer, a first color ink layer and a first adhesive layer stacked in this order from the substrate side, the first release layer comprising a wax material as a main component by weight, the first adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
the second color transfer layer comprising at least a second release layer, a second color ink layer and a second adhesive layer stacked in this order from the substrate side, the second release layer comprising a wax material as a main component by weight, the second adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
wherein the thickness d1 of the first release layer; the thickness d2 of the second color ink layer; the thickness d3 of the second adhesive layer; and the average particle size R of the particles contained in the second adhesive layer satisfy the following relation:
(d1+d2+d3)xc3x972 greater than R greater than d1+d3xe2x80x83xe2x80x83(I).
According to a second aspect of the present invention, there is provided a combination of a plurality of color thermal transfer recording media for forming a multi-color image by superimposing printing of a plurality of different color inks, comprising at least a first color thermal transfer recording medium and a second color thermal transfer recording medium,
the first color thermal transfer recording medium comprising a first substrate and a first color transfer layer provided on the first substrate, the first color transfer layer comprising at least a first release layer, a first color ink layer and a first adhesive layer stacked in this order from the substrate side, the first release layer comprising a wax material as a main component by weight, the first adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
the second color thermal transfer recording medium comprising a second substrate and a second color transfer layer provided on the second substrate, the second color transfer layer comprising at least a second release layer, a second color ink layer and a second adhesive layer stacked in this order from the substrate side, the second release layer comprising a wax material as a main component by weight, the second adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
wherein the thickness d1 of the first release layer; the thickness d2 of the second color ink layer; the thickness d3 of the second adhesive layer; and the average particle size R of the particles contained in the second adhesive layer satisfy the following relation:
(d1+d2+d3)xc3x972 greater than R greater than d1+d3xe2x80x83xe2x80x83(I).
According to a third aspect of the present invention, there is provided a method for forming a multi-color image by superimposing printing of a plurality of different color inks, comprising the steps of:
providing a color thermal transfer recording medium comprising a substrate, and at least a first color transfer layer and a second color transfer layer provided on the substrate in a side-by-side relation,
the first color transfer layer comprising at least a first release layer, a first color ink layer and a first adhesive layer stacked in this order from the substrate side, the first release layer comprising a wax material as a main component by weight, the first adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
the second color transfer layer comprising at least a second release layer, a second color ink layer and a second adhesive layer stacked in this order from the substrate side, the second release layer comprising a wax material as a main component by weight, the second adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
wherein the thickness d1 of the first release layer; the thickness d2 of the second color ink layer; the thickness d3 of the second adhesive layer; and the average particle size R of the particles contained in the second adhesive layer satisfy the following relation:
(d1+d2+d3)xc3x972 greater than R greater than d1+d3xe2x80x83xe2x80x83(I).
conducting a thermal transfer using the first transfer layer to foam a first color image, and
conducting a thermal transfer using the second transfer layer to form a second color image on the first color image.
According to a fourth aspect of the present invention, there is provided a method for forming a multi-color image by superimposing printing of a plurality of different color inks, comprising the steps of:
providing a combination of a plurality of color thermal transfer recording media comprising at least a first color thermal transfer recording medium and a second color thermal transfer recording medium,
the first color thermal transfer recording medium comprising a first substrate and a first color transfer layer provided on the substrate, the first color transfer layer comprising at least a first release layer, a first color ink layer and a first adhesive layer stacked in this order from the substrate side, the first release layer comprising a wax material as a main component by weight, the first adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
the second color thermal transfer recording medium comprising a second substrate and a second color transfer layer provided on the second substrate, the second color transfer layer comprising at least a second release layer, a second color ink layer and a second adhesive layer stacked in this order from the substrate side, the second release layer comprising a wax material as a main component by weight, the second adhesive layer comprising a binder comprising a thermoplastic resin as a main component by weight and particles dispersed in the binder,
wherein the thickness d1 of the first release layer; the thickness d2 of the second color ink layer; the thickness d3 of the second adhesive layer; and the average particle size R of the particles contained in the second adhesive layer satisfy the following relation:
(d1+d2+d3)xc3x972 greater than R greater than d1+d3xe2x80x83xe2x80x83(I).
conducting a thermal transfer using the first color transfer layer of the first color thermal transfer medium to foam a first color image, and
conducting a thermal transfer using the second color transfer layer of the second color thermal transfer medium to form a second color image on the first color image.